This invention concerns contact lenses adapted to ensure correction, through a single dioptric means, for both visual defects related to far range vision (miopia and hypermetropia), and visual defects related to near range vision (presbyopia).
Furthermore, this invention concerns the process for manufacturing said contact lenses, through use of any type of lathe, both numerically controlled and "duplicating" lathe, controlled by a computer or electronic data processing equipment, according to special process computer programs. As it is already known, in the lenses for conventional glasses, the possibility to see correctly both in the near distance range and in the far distance range, is provided by dividing said lenses in two parts, wherein the upper part enables far range vision while the lower part enables near range vision, owing to the eye motions relative to the lens. Therefore, said lenses are called bifocal lenses. Also known are trifocal and multifocal lenses, both with visible or invisible edge. As it should be apparent, this type of lens partitioning in two or more asymmetrical parts is not feasable in contact lenses, since the lens constantly follows the eye motions, and no relative displacements are possible. While striving to overcome said drawback with contact lenses, a compromise has been made, trying to exploit the capacity of the pupil to adapt to the different light conditions. Therefore, it has been contrived to divide the contact lens in two or more concentric areas having a different degree of spherical curvature, whereby the pupil, when expanding or contracting, can use the different areas, according to the light available, while being supported in this process by the discrimination and synthesis capacity of the brain. However, it has been noticed that said lenses having areas with different spherical curvature gave a blurred vision (for instance split vision) and the eye got easily tired.